1. Field of the Invention
The present invention relates to a toner including compound having a bisazo skeleton unit and a polymer resin unit as a pigment dispersant and used for electrophotography, electrostatic recording, electrostatic printing, or toner jet recording.
2. Description of the Related Art
For example, Japanese Patent No. 03917764 discloses a method using an azo pigment as a colorant for a toner. In the case where such an azo pigment is used as the colorant for a toner, the pigment needs to be finely dispersed in a binder resin or a polymerizable monomer in the toner in order to improve spectral characteristics such as coloring power and transparency. Unfortunately, usually, a fine azo pigment is likely to cause crystal growth or dislocations due to a thermal history and contact with a solvent in a dispersing step or a production step subsequent thereto, undesirably reducing the coloring power or the transparency. Further, in a process of producing a toner using the azo pigment, particularly in a process of producing a toner by a polymerization method, the fine azo pigment aggregates again to increase viscosity of a pigment dispersion liquid.
In order to improve these problems, a variety of pigment dispersants has been proposed. For example, a polymer dispersant has been disclosed in which a site having affinity with an azo pigment as a colorant covalently bonds to an oligomer or polymer site having affinity with a solvent and a binder resin (see Japanese Patent No. 03984840). Further, an example has been disclosed in which a comb polymer dispersant known as Solsperse (registered trademark) and having an acid or basic site is used (see International Application No. WO 99/42532).
Meanwhile, recently, higher image quality of an output image has been desired. For this reason, image defects such as image fogging, i.e., a toner developed in a non-image portion and an uneven density of an image caused by low transfer efficiency of the toner need to be solved.